Is driving shirtless illegal?

Not for me. If you are exposing your nipples it would be. You don't have a 'reasonable expectation of privacy' in your vehicle and it would be indecent exposure.
Can you drive through my neighborhood?
It is in Panama. Why, I don't know.
for guys , not illegal. for gals, ticket time
It's not illegal for the guys to drive shirtless, but most guys wear them, because they can't make those beer or KEG runs. The large sign on the Store says so: NO SHIRT, NO SERVICE!

Georgetslc, does the Shirtless society sell calenders? This girl wants 100% GRADE 'A' USDF approved Beef please!
Nah its not illegal. Guys body exposed aint illegal

Not anywhere in the United States, so far as I know. I'll explicitly ask my brothers at the Shirtless Lifestyle Yahoo! Group, but I believe it would have come up before there or similar places if there were such legislation.